Apparatus for making helical conveyor blades by edgewise bending and squeezing rolls



Dec. 10, 1957 T. L. MAYRATH 2,815,790

APPARATUS FOR MAKING HELICAL. CONVEYOR BLADES BY EDGEWISE BENDING ANDSQUEEZING ROLLS Filed June 3, 1955 ATTORNEY United States PatentAPPARATUS FOR MAKING HELICAL CONVEYOR BLADES BY EDGEWISE BENDING ANDSQUEEZ- ING ROLLS Thomas L. Mayrath, Dodge City, Kans.

Application June 3, 1955, Serial No. 512,970 3 Claims. (Cl. 153--2) Thisinvention pertains to the making of helical shapes from flat stripstock, and particularly to the formation of helical conveyor blades froma continuous flat strip of metal or the like.

In the past, helical conveyor blades and similar helical elements havebeen successfully formed from a continuous strip of fiat stock bybending the flat strip in, or nearly in, its own plane, and thereafteraxially stretching the spiral'thus formed to the desired degree forapplication to a central shaft. Much the same result has beenaccomplished by the passage of the flat strip between two squeeze rollswhose working surfaces contacting the strip across its width are notparallel. As a result of the non-parallelism of the two rolls, as thestrip as squeezed by the rolls and one of its edges is squeezed orstretched more than is the other. Each of these methods of obtaining aspiral-from a strip of flat stock is satisfactory within certain limits.However, each is quite limited with respect to the degree of pitch thatmay be obtained thereby, due to the elastic limits of the material andhardening of the material due to so-called cold-working. If in either ofthese prior methods it is attempted to obtain a degree of bending orcurvature that is greater than what has proved to be an inconvenientlysmall magnitude, the material of the strip tends to crack and break.This is particularly true where the strip stock is of substaritialwidth, and where the outside diameter of the helix is considerablygreater than the inside diameter.

The present invention overcomes the limits just mentioned, by applyingalternate tension and compression loads to the strip in directions whichare perpendicular to one another. Since in the production of helicalmembers from flat stock, it is necessary to increase the effectivelength of one edge of the stock many times more than the effectivelength of the opposite edge, the problem of fracture and cold-workingbecomes apparent. In the case of forming a helix whose inside (shaft)diameter is to be 1", and whose outside diameter is to be 5", with ahelical pitch of 5", the required final length of the outside edge ofthe strip (per foot of helix) will be 39.5", while the correspondinglength of the inside edge will be 14.16. This amount of cold stretchingwill produce fracture cracks in most materials, even allowing for thefact that a part of the ratio of lengths is absorbed by incidentalcompression of the inner edge of the stock. The invention makes itfeasible to accomplish such a helix, and even more strongly curved ones,without producing these fractures. Actual helices having outer-toinne'rlength ratios of as much as 8 to 1 have been satisfactorily accomplishedusing the present invention, without the necessity for any heating ofthe strip itself.

In general, the improved method of the invention involves firstcontinuously bending the metal strip in its own plane to an intermediatecurvature, followed by the selective application of squeezing orcompressional force to the outer edge of the curved strip, thiscompression being'di'rected across the thickness of the strip and henceat a right angle to the plane in which the original curva ture wasproduced. The degree of compression applied at this stage is such as toestablish approximately the final desired outside diameter of the helix,but since the subsequent operation of bending this spiral in atransverse direction in order to form a helix of the desired final pitchwill usually slightly further reduce the outside diameter, allowance ismade for this factor in establishing the degree of compression. To carryout this process most conveniently at production rates, there isprovided novel apparatus in which the strip of flat stock is subjectedto the bending and squeezing processes, in turn, with subsequent lateralbending of the bent strip in order to form the helix. It is in thealternate bending and squeezing of the strip that the advantages of theinvention are obtained, since it has been found that a strip of asuitable metallic material may be cold-formed into a spiral ofrelatively many more turns per unit length by this alternate bending andsqueezing process, and to a smaller final radius, without exceeding theelastic limits thereof than can be obtained by merely bending orsqueezing alone. When the desired degree of curvature is thusaccomplished the spiral strip is finally bent in a direction transverseto the direction of previous bending in order to convert the spiral intothe desired helix. The degree of transverse bending is controlled, bothat the point of first bending the strip out of its own' plane and at apoint spaced a suitable distance down along the helix that is thusformed, in order to fix the final pitch of the helix as desired.

Other objects and a clearer understanding of the in vention will berealized by referring to the following detailed description of apreferred form of the improved method and apparatus, taken inconjunction with the accompanying drawings, in which:

Fig. 1 is a side elevation view of a preferred apparatus for carryingout the invention, portions being broken away for clarity.

Fig. 2 is a view of the same apparatus from above, With parts insection.

Fig. 3 is a front elevation of the final pitch-determining mechanism ofthe invention, showing the relationship of the other apparatus thereto,and partly in section on line 33 of Fig. 2.

In Figs. 1 and 2; the strip 10 of fiat stock such as steel is'sh'ownentering between the spaced guide plates 12 and 14' which serve torestrain the strip 10 from buckling as a result of the bending forces tobe applied. The guide plates 12 and 14 are so positioned with respect toeach other that the spacing therebetween is just sufficient to allow thestrip 10 to pass. Obviously, the guide plates may be made adjustable, orcan be replaced as a unit in order to adapt the guideway to differentwidths and thicknesses of the strip material. Mounted upon and extendingbetween the guide plates 12 and 14 are rollers 16 and 18 which bearagainst the upper edge of the strip 10 as it passes between the plates12 and 14. Similarly mounted in the guides is a third roller 20 whichbears against the lower edge of the strip 10. Roller 20 has spacedflanges (one is shown at 21) which bear against opposite faces of strip10. The three rollers 16, 18 and 20 define the path of travel of thestrip 10 between the guide plates 12 and 14. A fourth roller 22 isadjustably mounted by means of arm 23 with respect to the framework orpillar 24 upon which is fixedly mounted the guide assembly comprisingthe plates 12 and 14 and rollers 16, 18 and 20. Roller 22 is positionedin the plane of the strip 10 and at a position in the vertical planewhich is below that of the upper edge of the strip in the guide. As thestrip 10 is initially fed through the machine to begin the operationthereof, it is fed under the roller 22 in such manner that the upperedge of the strip bears against the roller'2 2, causingthe strip 10 tobend in its own plane.

3 This bend is the first of the three major operations performed uponthe strip in the process of transforming it from a strip of flat stockto the spiral or helical configuration required.

After the strip has been subjected to the above described bending, it isfed between two squeeze rolls 26 and 28, having conical working facesand 32, respectively. Rolls 26 and 28 are journalled in rigid bearings34 and 36, which bearings are mounted upon a common frame member ofsufficient bulk and strength to support the rolls 26 and 28 during theoperation of the machine. As may be seen in Fig. 2, the working faces 30and 32 of rolls 26 and 28 are not parallel, as they contact strip 10,but are farther apart at their tips. Roll 28 is driven from motor shaft38 by means of spur gears 40 and 42 in such direction that strip 10 isdrawn in a downward direction by frictional engagement with the workingface 32. Such frictional engagement is provided by the relativepositioning of the working faces 30 and 32 which are adapted to squeezethe strip 10 as it passes between them. Clearly, both rolls 26 and 28could be power driven if desired. The rolls 26 and 28 are adjustablymounted with respect to each other, and may be adjusted both as to thespacing and the angle between them by means such as the turnbuckles 44and 46. It will be understood that one or both of the bearings 34 and 36is adjustably mounted upon their common frame member. As was previouslystated, the working faces 30 and 32 of the rolls 26 and 28 are notparallel as they contact strip 10, but are farther apart at the tips. Asthe strip 10 is caused to pass between the working faces 30 and 32 dueto the rotation of rolls 26 and 28, a further bending takes place due tothe relatively greater elongation of that edge of strip 10 which isfarther from the tips of faces 30 and 32. This edge of strip 10 is theupper edge as the strip is fed between guide plates 12 and 14 and underroll 22, and is the outer peripheral edge of the strip after the bend isproduced.

Subsequent to the squeezing step that is thus accomplished between theworking surfaces of the squeeze rolls 26 and 28, the strip 10 is bentout of its own plane by reason of the action of the roller 48, as bettershown in Fig. 3. Roller 48 is mounted for free rotation upon an arm 50suitably supported as by pillar 24, and bears against the inner orshorter edge of the bent strip. As may be seen in Fig. 1, arm 50 isadjustably mounted on the pillar as by means of pivot bolt 52 andadjusting means comprising the threaded shaft 54, bracket 56 on pillar24 and nut 58. The pivotal position of arm 50, and hence the position ofthe roller 48, determines the approximate pitch of the spiral to beproduced, the precise final pitch being fixed by the positioning of theguide pin 60 which is fixedly mounted as on head 62 of a post 64. Post64 is adjustably mounted with respect to framework pillar 24 by anysuitable means, such as a threaded shaft and nut, whereby thelongitudinal distance along the spiral between the pillar 24 and thepost 64 may be varied. As may be seen in Fig. 3, the inner or shorteredge of the strip 10 bears on pin 60 at the head 62 and the positioningof the post 64 and its pin is such that an axial stretching of the helixis accomplished. Thus the combined action of the roller 48 and the pin60 constitute the third major operation, namely that of forming a helixfrom the bent and squeezed flat strip.

The operation of the apparatus of the invention is now obvious. As theflat strip 10 is fed into the machine, it enters the passage between theguide plates 12 and 14 and is subjected to a bending action in its ownplane by reason of the relative positioning of the rollers 16, 18, 20and 22. The degree of bending accomplished at this first bend iscontrolled by the positioning of the roller 22.

A second or squeezing stage is accomplished when the strip 10 passesbetween the non-parallel strip-contacting portions of working faces 30and 32 of rolls 26 and 28. Power is supplied to the roll or rolls insuch rotational sense that the strip 10 is drawn down between the rolls,

The degree of bending accomplished at this second or squeezing stage iscontrolled by the angle between the rolls 26 and 28. If, for instance, agreater bend is desired, the angle between the roll axes is decreasedand the nonparallelism of the working surfaces 30 and 32 is thusincreased, increasing the difference in the relative magnitude ofsqueezing to which the opposite lateral edges of the strip 10 aresubjected. An increase in the angle between rolls 26 and 28 would havethe opposite result. If it were to be found also desirable to compressthe strip 16 generally, in addition to differentially between the edges,the rolls 26 and 28 may be moved bodily closer together. Also, thesqueeze rolls may be moved with respect to each other with or withoutchanging the angle therebetween, in order that strips of differentthicknesses may be accommodated.

As a third step and final step, the strip is bent in a directiontransverse to the plane of bending by the roller 48, which bears againstthe inner or shorter edge of the strip. There is thus formed a spiralhelix, the pitch of which is approximately that of the finished product.The final pitch is accurately determined by the positioning of a guidepost 64 which carries the head 62 and pin 60. The inner edge of thespiral formed by the strip 10 is made to bear against the pin 60, sopositioned along the helix as to determine finally the pitch initiallyapproximated by the position and angulation of roller 48. The inside andoutside diameters of the finished spiral are indicated by the legends IDand OD in Fig.3.

It will be seen from the above that the helix produced is especiallywell suited for conveyors of the screw type in which the helix issecured about a central shaft, as by welding the turns to such shaft.The reduction in thickness of the ribbon stock is entirely at the outeredge, so that the thickness of the finished helical ribbon increases asone proceeds from the outer edge toward the helical axis. This not onlymaintains adequate stock at the center for fastening purposes, but forthe usual case in which the conveyor flight in operation is embedded inthe material being conveyed, provides a good distribution of materialradially of the flight to resist the reaction moments produced by theconveying operation. The design, from this radial viewpoint, approachesthe constant-strength beam of tapered thickness.

While the process has been described in detail in connection with aparticular apparatus for carrying it out, and which apparatus is itselfpossessed of novel advantages, it is clear that the process can also becarried out without special machinery. Thus, the initial bending can beaccomplished by hand if desired, and the differential squeezing by ahammering operation rather than by continuous compression. The lateraldeflection of the turns need not be continuous, but can be introducedfrom time to time as the final desired curvature is approached, toestablish the desired pitch. Apparatus can readily be envisioned whichwould substitute hammering or other compressional forces for the rollingoperation, although the latter is presently believed to presentcommercial advantages. The feeding drive need not be applied at thesqueeze rolls, but the strip could be fed by subsidiary driving means ofknown type.

Since the ribbon or strip must be bent edgewise to produce the desiredflat helical turns, it will be understood that the term in its ownplane" as used herein refers to the plane perpendicular to the thicknessdimension of the original strip stock. The invention is not intended tobe limited to the details described above and shown in the drawings,which are given by way of example of the best way known for practisingthe invention, except as such limitations may be required by the termsof the appended claims.

What is claimed is:

1. Apparatus for forming a helix from flat metallic strip stock,comprising bending rolls for guiding the strip into a curved shape inits own plane, a pair of squeezing rolls for receiving the curved striptherebetween and for diflerentially squeezing the outer curved edge toincrease the curvature, and means for directing the strip leaving saidrolls laterally of the central plane of said rolls to form a helicalshape.

2. Apparatus in accordance with claim 1, including means for driving atleast one of said squeezing rolls to effect feeding of the strip.

3. Apparatus in accordance with claim 1, in which said squeezing rollshave conical facing surfaces so disposed as to approach one anothercloser at the position between their surfaces occupied by the outercurved edge of the entering strip.

References Cited in the file of this patent UNITED STATES PATENTS EvansSept. 10, 1878 Reinnan Aug. 24, 1886 Zimmermann Jan. 19, 1926 GredellDec. 10, 1929 Dorndorf Sept. 9, 1930 Bundy Feb. 7, 1933 Pickard Dec. 12,1933 Nigro Nov. 20, 1934 Fulson Nov. 11, 1941 Stikeleather Apr. 17, 1945

